The present invention relates to mechanical scanheads. In particular, it relates to a mechanical scanhead of the type used in medical electronic diagnostic ultrasound equipment.
Ultrasound is a non-invasive technique for generating image scans of interior body organs. As is well known in the art, there are a variety of types of ultrasound transducers. These include elongated transducers, such as phased array transducers and linear array transducers which are fully electronic in beam forming and directing, and various types of spherical transducers and annular arrays, which are typically scanned mechanically.
Mechanical scanheads typically utilize two techniques for generating sector scans. The first technique, which requires a plurality of transducers, is the rotating scanhead unit, in which the various transducers are rotated through 360 degrees and are turned on in succession over a sector which corresponds to the sector being scanned. The second type of mechanical scanhead is an oscillating scanhead, sometimes called a "wobbler". In either type of mechanical scanhead, drive means, such as a motor, must be connected to the transducer in order to impart mechanical movement to the rotor. In typical mechanical scanheads, of the type heretofore used, the motor drive means is in a dry ambient whereas the ultrasound transducer is typically immersed in an acoustic coupling medium such as mineral oil. A problem which has heretofore existed with mechanical scanheads, especially those which require a plurality of transducers, is that they are very expensive to manufacture due to the critical alignment of the various parts from which they are made. In addition, there has always been a problem with the seals between the dry portion of the scanhead, in which the motor is located, and the wet portion of the scanhead in which the transducer is located. Heretofore, there has also been a problem with determining the exact position of the ultrasound transducer to a high degree of accuracy when the encoder was mounted on the motor shaft. This has required that very accurate, and expensive, precision gearing be used to connect the scanhead to the motor. As a result of the use of both a wetted area and a dry area and the use of precision gears, mechanical scanheads have typically been rather large when compared to phased array transducers. The excessive size of mechanical scanheads has made them somewhat unwieldy to use in some applications. Consequently, a less expensive, more reliable, and smaller mechanical scanhead would be highly desirable.